How’s this for a culture shock? All my adult life, I have regarded French shop staff as the ultimate miserables. Suddenly I discover that it was I who started the cycle of rudeness.

The problem was that I never once said “Hello”. Which is why the people serving me invariably pursed their lips and gave me my change in centime coins.

In shops and banks - even at supermarket checkouts - the French observe a formality that we frequently dispense with. On entering, they greet the staff and other customers, not just with “Bonjour”, but with “monsieur” and “madame” attached. And when they leave, they say goodbye.

You already knew this? You have always known it? Everyone you know has always known it? Well no one told me!

For an entire decade, from eight to 18, someone was usually trying to teach me French. Did they mention the correct way to enter a patisserie? Not once.

Retail etiquette never came up in discussions about Anouilh’s Antigone, and if Verlaine ever did a big weekly shop, he definitely didn’t refer to it in any of his fey poems. I do dimly recall covering the ubjunctive mood. But putting the cashier at the Intermarche in the right mood? Non.

In my experience - years later, when I actually went to France - cashiers were never in the right mood. They were just in a mood. Had I said “le” instead of “la”? Were my subjunctives sub-standard? I even tried smiling. But all I got was That Look.

Then quite recently, and almost 30 years after my last formal French lesson, I was browsing through a book for Americans relocating to France when I stumbled on it.

Greetings were essential, said the author. Not to say hello was positively offensive - upsetting, even.

I’d always assumed that the man who greeted the entire wine shop was a wino, and that the shopkeeper who said “Au revoir monsieur, madame”, was making a point.I never dreamed it was obligatory.

I tried it, of course, on my very next visit, and I’m happy to report that it worked a treat. In fact, so positive was the feedback that soon I had to be restrained from entering shops simply to greet the staff. It’s a shame about the missing years, though. What else, I wonder, did no one think to tell me?